/* idled.c - daemon for handling IMAP IDLE notifications
 *
 * Copyright (c) 1994-2008 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Carnegie Mellon University
 *      Center for Technology Transfer and Enterprise Creation
 *      4615 Forbes Avenue
 *      Suite 302
 *      Pittsburgh, PA  15213
 *      (412) 268-7393, fax: (412) 268-7395
 *      innovation@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <sys/types.h>
#include <sysexits.h>
#include <syslog.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <errno.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <signal.h>
#include <fcntl.h>

#include "idlemsg.h"
#include "global.h"
#include "mboxlist.h"
#include "xmalloc.h"
#include "hash.h"

extern int optind;
extern char *optarg;

static int verbose = 0;
static int debugmode = 0;
static time_t idle_timeout;

struct ientry {
    struct sockaddr_un remote;
    time_t itime;
    struct ientry *next;
};
static struct hash_table itable;

EXPORTED void fatal(const char *msg, int err)
{
    if (debugmode) fprintf(stderr, "dying with %s %d\n",msg,err);
    syslog(LOG_CRIT, "%s", msg);
    syslog(LOG_NOTICE, "exiting");

    cyrus_done();

    exit(err);
}

static int mbox_count_cb(const mbentry_t *mbentry __attribute__((unused)), void *rockp)
{
    int *ip = (int *) rockp;
    (*ip)++;

    return 0;
}

/* remove an ientry from list of those idling on mboxname */
static void remove_ientry(const char *mboxname,
                          const struct sockaddr_un *remote)
{
    struct ientry *t, *p = NULL;

    t = (struct ientry *) hash_lookup(mboxname, &itable);
    while (t && memcmp(&t->remote, remote, sizeof(*remote))) {
        p = t;
        t = t->next;
    }
    if (t) {
        if (!p) {
            /* first ientry in the linked list */

            p = t->next; /* remove node */

            /* we just removed the data that the hash entry
               was pointing to, so insert the new data */
            hash_insert(mboxname, p, &itable);
        }
        else {
            /* not the first ientry in the linked list */

            p->next = t->next; /* remove node */
        }
        free(t);
    }
}



static void process_message(struct sockaddr_un *remote, idle_message_t *msg)
{
    struct ientry *t, *n;
    int r;

    switch (msg->which) {
    case IDLE_MSG_INIT:
        if (verbose || debugmode)
            syslog(LOG_DEBUG, "imapd[%s]: IDLE_MSG_INIT '%s'",
                   idle_id_from_addr(remote), msg->mboxname);

        /* add an ientry to list of those idling on mboxname */
        t = (struct ientry *) hash_lookup(msg->mboxname, &itable);
        n = (struct ientry *) xzmalloc(sizeof(struct ientry));
        n->remote = *remote;
        n->itime = time(NULL);
        n->next = t;
        hash_insert(msg->mboxname, n, &itable);
        break;

    case IDLE_MSG_NOTIFY:
        if (verbose || debugmode)
            syslog(LOG_DEBUG, "IDLE_MSG_NOTIFY '%s'", msg->mboxname);

        /* send a message to all clients idling on mboxname */
        t = (struct ientry *) hash_lookup(msg->mboxname, &itable);
        for ( ; t ; t = n) {
            n = t->next;
            if ((t->itime + idle_timeout) < time(NULL)) {
                /* This process has been idling for longer than the timeout
                 * period, so it probably died.  Remove it from the list.
                 */
                if (verbose || debugmode)
                    syslog(LOG_DEBUG, "    TIMEOUT %s", idle_id_from_addr(&t->remote));

                remove_ientry(msg->mboxname, &t->remote);
            }
            else { /* signal process to update */
                if (verbose || debugmode)
                    syslog(LOG_DEBUG, "    fwd NOTIFY %s", idle_id_from_addr(&t->remote));

                /* forward the received msg onto our clients */
                r = idle_send(&t->remote, msg);
                if (r) {
                    /* ENOENT can happen as result of a race between delivering
                     * messages and shutting down imapd.  It indicates that the
                     * imapd's socket was unlinked, which means that imapd went
                     * through it's graceful shutdown path, so don't syslog. */
                    if (r != ENOENT)
                        syslog(LOG_ERR, "IDLE: error sending message "
                                        "NOTIFY to imapd %s for mailbox %s: %s, "
                                        "forgetting.",
                                        idle_id_from_addr(&t->remote),
                                        msg->mboxname, error_message(r));
                    if (verbose || debugmode)
                        syslog(LOG_DEBUG, "    forgetting %s", idle_id_from_addr(&t->remote));
                    remove_ientry(msg->mboxname, &t->remote);
                }
            }
        }
        break;

    case IDLE_MSG_DONE:
        if (verbose || debugmode)
            syslog(LOG_DEBUG, "imapd[%s]: IDLE_MSG_DONE '%s'",
                   idle_id_from_addr(remote), msg->mboxname);

        /* remove client from list of those idling on mboxname */
        remove_ientry(msg->mboxname, remote);
        break;

    case IDLE_MSG_NOOP:
        break;

    default:
        syslog(LOG_ERR, "unrecognized message: %lx", msg->which);
        break;
    }
}


static void send_alert(const char *key,
                       void *data,
                       void *rock __attribute__((unused)))
{
    struct ientry *t = (struct ientry *) data;
    struct ientry *n;
    idle_message_t msg;
    int r;

    msg.which = IDLE_MSG_ALERT;
    strncpy(msg.mboxname, ".", sizeof(msg.mboxname));


    for ( ; t ; t = n) {
        n = t->next;

        /* signal process to check ALERTs */
        if (verbose || debugmode)
            syslog(LOG_DEBUG, "    ALERT %s", idle_id_from_addr(&t->remote));

        r = idle_send(&t->remote, &msg);
        if (r) {
            /* ENOENT can happen as result of a race between shutting
             * down idled and shutting down imapd.  It indicates that the
             * imapd's socket was unlinked, which means that imapd went
             * through it's graceful shutdown path, so don't syslog. */
            if (r != ENOENT)
                syslog(LOG_ERR, "IDLE: error sending message "
                                "ALERT to imapd %s for mailbox %s: %s, "
                                "forgetting.",
                                idle_id_from_addr(&t->remote),
                                msg.mboxname, error_message(r));
            if (verbose || debugmode)
                syslog(LOG_DEBUG, "    forgetting %s", idle_id_from_addr(&t->remote));
            remove_ientry(key, &t->remote);
        }
    }
}

static void shut_down(int ec) __attribute__((noreturn));
static void shut_down(int ec)
{
    hash_enumerate(&itable, send_alert, NULL);
    idle_done_sock();
    cyrus_done();
    exit(ec);
}

int main(int argc, char **argv)
{
    char *p = NULL;
    int opt;
    int nmbox = 0;
    int s;
    struct sockaddr_un local;
    fd_set read_set, rset;
    int nfds;
    struct timeval timeout;
    pid_t pid;
    char *alt_config = NULL;

    p = getenv("CYRUS_VERBOSE");
    if (p) verbose = atoi(p) + 1;

    while ((opt = getopt(argc, argv, "C:d")) != EOF) {
        switch (opt) {
        case 'C': /* alt config file */
            alt_config = optarg;
            break;
        case 'd': /* don't fork. debugging mode */
            debugmode = 1;
            break;
        default:
            fprintf(stderr, "invalid argument\n");
            exit(EX_USAGE);
            break;
        }
    }

    cyrus_init(alt_config, "idled", 0, 0);

    /* Set inactivity timer (minimum is 30 minutes) */
    idle_timeout = config_getduration(IMAPOPT_TIMEOUT, 'm');
    if (idle_timeout < 30 * 60) idle_timeout = 30 * 60;

    /* count the number of mailboxes */
    mboxlist_allmbox("", &mbox_count_cb, &nmbox, /*flags*/0);

    signals_set_shutdown(shut_down);
    signals_add_handlers(0);

    /* create idle table -- +1 to avoid a zero value */
    construct_hash_table(&itable, nmbox + 1, 1);

    if (!idle_make_server_address(&local) ||
        !idle_init_sock(&local)) {
        cyrus_done();
        exit(1);
    }
    s = idle_get_sock();

    /* fork unless we were given the -d option or we're running as a daemon */
    if (debugmode == 0 && !getenv("CYRUS_ISDAEMON")) {

        pid = fork();

        if (pid == -1) {
            perror("fork");
            exit(1);
        }

        if (pid != 0) { /* parent */
            exit(0);
        }
    }
    /* child */


    /* get ready for select() */
    FD_ZERO(&read_set);
    FD_SET(s, &read_set);
    nfds = s + 1;

    for (;;) {
        int n;
        int sig;

        sig = signals_poll();
        if (sig == SIGHUP && getenv("CYRUS_ISDAEMON")) {
            /* XXX maybe don't restart if we have clients? */
            syslog(LOG_DEBUG, "received SIGHUP, shutting down gracefully");
            shut_down(0);
        }

        /* check for shutdown file */
        if (shutdown_file(NULL, 0)) {
            /* signal all processes to shutdown */
            if (verbose || debugmode)
                syslog(LOG_DEBUG, "Detected shutdown file");
            shut_down(1);
        }

        /* timeout for select is 1 second */
        timeout.tv_sec = 1;
        timeout.tv_usec = 0;

        /* check for the next input */
        rset = read_set;
        n = signals_select(nfds, &rset, NULL, NULL, &timeout);
        if (n < 0 && errno == EAGAIN) continue;
        if (n < 0 && errno == EINTR) continue;
        if (n == -1) {
            /* uh oh */
            syslog(LOG_ERR, "select(): %m");
            close(s);
            fatal("select error",-1);
        }

        /* read and process a message */
        if (FD_ISSET(s, &rset)) {
            struct sockaddr_un from;
            idle_message_t msg;

            if (idle_recv(&from, &msg))
                process_message(&from, &msg);
        }

    }

    /* NOTREACHED */
    shut_down(1);
}